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4. Close both valves on the manifold gauge set.
Turn the vacuum pump off and observe the
gauges. The system should hold the vacuum
within 5 cm Hg (2.0 in. Hg) of the optimal vac-
uum for 5 minutes. If the vacuum does not hold,
moisture may still be present in the system.
Repeat the previous step. If the vacuum still
does not hold, a leak may be present in the sys-
tem. Find the source of the leak, repair, and
evacuate the system, again.
Meters (Feet) Above Sea Level
NOTE: The chart indicates the expected gauge readings at altitude to obtain the optimal vacuum.
N4-36
TABLE 2. ALTITUDE VACUUM VARIATIONS
Altitude
0
305 (1000)
610 (2000)
914 (3000)
1219 (4000)
1524 (5000)
1829 (6000)
2134 (7000)
2438 (8000)
2743 (9000)
Operator Comfort
NOTE: In some cases, 45 minutes of evacuation may
not be sufficient to vaporize all of the moisture and
draw it out of the system. If it has been verified that
no system leaks exist and gauge readings increase
after 45 minutes, extend the evacuation time to
ensure total moisture removal.
Optimal Vacuum
Cm Hg. (In. Hg.)
76.0 (29.92)
73.5 (28.92)
70.7 (27.82)
68.1 (26.82)
65.6 (25.82)
63.3 (24.92)
60.8 (23.92)
58.5 (23.02)
56.4 (22.22)
54.2 (21.32)
10/06 N04031
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